1. Field of the Invention
The present invention relates to a system and a method for manufacturing a surgical guide, and more particularly, to a system and a method which can precisely and quickly manufacture a surgical guide with a dental cast model.
2. Description of the Related Art
In order to help patients with missing teeth to restore their chewing function, dental implant placement is an effective and mature treatment. Generally, dental implant treatment uses a titanium-based alloy stud placed in the jawbone to imitate the root of a natural tooth. After some time, when the osseointegration between the jawbone and the dental implant is completed, subsequent prosthetic treatment proceeds. Compared with the traditional tooth bridge treatment, which requires that the healthy neighboring teeth be trimmed to support the bridge, dental implant treatment does not affect the neighboring teeth and is obviously a superior and more efficient treatment.
The position and the direction of the dental implant have great impacts on the quality of the treatment. An improper position of the implant will cause excessive stress when the patient is chewing, and the implant could eventually come out due to bone loss. The appropriate implant position depends on two factors: thorough planning of the surgery and precise drilling during the surgery. In surgery planning, the dentist must use the patient's cast model and X-ray radiographs to plan for the optimal implant position. The cast model provides external information for the dentist to evaluate the patient's occlusion status to achieve better results in the treatment. On the other hand, X-ray radiographs can provide internal anatomical information on the teeth, jawbone, alveolar nerve, paranasal sinus, etc. While drilling during the surgery, the dentist has to rely on his/her clinical experience and surgical skill to operate successfully. Therefore, the dentist's ability to perform stable drilling and strong perception of the 3D space can affect the quality of the surgery. An experienced dentist often uses the neighboring teeth and the exposed bone ridge as references, guided by the surgery plan, to place the implant in the optimal position.
As technology advances, computed tomography (CT) and surgical guides are now applied in dental implant surgery to improve the quality thereof. Compared to traditional planar imaging methods such as periapical film or panoramic imaging, CT provides a 1:1 undistorted image of the patient's oral anatomy. Therefore, the dentist can use the CT image with 3D imaging software to develop a surgery plan more accurately and then, can manufacture a corresponding surgical guide to guide the drill in order to place the implant in the optimal position. The surgical guide is usually made out of dental resin materials by forming a crown across the neighboring teeth. A metal ring is disposed at the implant position, and guiding sleeves of different apertures are used during the surgery to accommodate drill bits of different sizes. The CT-based surgical guide not only provides stability during drilling but also ensures placement in the optimal implant position prescribed in the surgery plan by the 3D imaging software.
A traditional manufacturing process for a CT-based surgical guide is illustrated below:
Step 1: Manufacturing a CT scan appliance. The CT scan appliance is manufactured out of dental resins and functions like a removable crown, which comprises a plurality of radiopaque markers. The image of the marker will appear in the CT image of the patient to provide the spatial association between the CT image and the surgical guide manufacturing system. Hence, the implant position planned in 3D imaging software can be transferred to the surgical guide system in order to manufacture the guide accurately. In addition to the markers, the CT scan appliance can also include wax-up information made of barium sulfate material to provide the ideal prosthetic information as the guideline for the implant placement.
Step 2: The patient wears the CT scan appliance for CT scan.
Step 3: Using 3D imaging software for surgery planning. The dentist uses imaging software to load the CT images of the patient to show the anatomical image of the jawbone around the surgery area. The anatomical information and the ideal prosthetic information of the CT scan appliance help the dentist to determine the optimal implant position, which will meet the occlusion demand but also will provide a stable foundation for implant placement as well. In addition to the dental prosthetic and jawbone information, scanning data of the gum surface can also be loaded to provide a more comprehensive 3D virtual reality of the patient's oral cavity.
Step 4: Transferring the planning to manufacture the surgical guide. First of all, a position registration must be obtained between the image space (CT image) and physical space (manufacturing system). The registration is obtained by the help of the markers of the CT scan appliance. By identifying the positions of the markers in the CT image and measuring the positions of the markers in physical space, the spatial transformation between the image and physical spaces can be calculated to facilitate the registration. Once registered, the planned implant position in the imaging software can be precisely transferred to the surgical guide manufacturing system for fabrication. Currently, there are two types of techniques for manufacturing CT surgical guides: rapid prototyping and CNC drilling. The rapid prototyping technique is disclosed in U.S. Pat. No. 5,768,134, while the CNC drilling technique is disclosed in U.S. Pat. Nos. 5,967,777, 6,296,483B1, and 6,814,575 B2.
Although the CT surgical guide technique can provide a way for improving the quality of the implant treatment, it is not widely used in clinical cases. One of the reasons is that dentists are not familiar with 3D imaging software for surgery planning. In fact, dentists spend most of the time using tools in the real environment of the patient's oral cavity and the corresponding cast model. They are not trained to use the computer mouse to manipulate virtual images in the complicated 3D imaging software. At present, most dentists use plaster cast models and X-ray radiographs, including CT images, for surgery planning. Although dentists have to mentally map relationships between the cast model and the images themselves, the cast model provides a closer situation to the real condition of the patient's oral cavity as compared with the 3D virtual reality provided by software. Therefore, this invention proposes a dental implant surgery planning system based on the cast model in U.S. Patent Publication No. 2008-0193896. The system navigates on the cast model by providing a real time 3D jawbone image corresponding to the interested location on the cast model. The association eliminates the burden of the mental conversion between the anatomical image and the location on the cast model for dentists. Another disadvantage of the current surgical guide manufacturing technique is that surgery planning and guide manufacturing are performed separately, When dentists finish a surgery plan, they have to send the surgery plan to a third party service for manufacture of the surgical guide. It is time consuming and, besides, it is not possible to verify the accuracy of the surgical guide, making it less acceptable in actual application. Therefore, it is desirable to integrate the dental implant surgery planning and the surgical guide manufacturing into one system to improve the accuracy of the guide and to reduce the time required for manufacturing.
Therefore, it is necessary to develop an integrated surgical guide manufacturing system to provide the familiar dental implant planning environment for dentists or dental technicians and also to generate a precise surgical guide promptly.